The Age of Mammals in Japan: After the dinosaurs came the Desmostylians

The Yomiuri ShimbunA skeletal exhibit of a desmostylian in the Osaka Museum of Natural History

April 4, 2013

[Jiji Press]

Desmostylians, a group of extinct mammals with unique teeth that looked like bundles of pipes, lived “essentially” in water, a study by Japanese and German researchers has suggested.

Much about the mammals, thought to have existed 10 million to 30 million years ago, remains a mystery, including the cause of their extinction. They had been believed to be aquatic or semiaquatic to some extent. Their fossils have been discovered in Japan and on the western coast of North America.

In an article published in the online scientific journal PLOS One on Wednesday, the researchers, including people from the Osaka Museum of Natural History and the University of Bonn, concluded that “all desmostylians had achieved an essentially, if not exclusively, aquatic lifestyle.”

The researchers analyzed the inner structures of desmostylian fossil bones and compared them with those of 60 existing mammals using computerized tomography scan technology as well as microscopes.

The study found that the desmostylian species Behemotops, Paleoparadoxia and Ashoroa were likely “shallow water swimmers,” with dense and heavy bones like those of dugongs and manatees.